SU943203A1 - Method for detecting iron of hydroxides - Google Patents

Description

one

This invention relates to analytical chemistry and concerns a method for determining iron hydroxides in oxidized iron ores.

A known method for the determination of iron hydroxides in the presence of hematite, based on thermal dissociation (calcination) of iron hydroxides, in which all hydrated forms of iron are dehydrated. From the amount of water lost during calcination, the stoichiometrically associated with it the amount of hydroxide is calculated.

Applied to oxidized iron ores, this method gives an error of + -6 abs. due to the presence of kaolin, scapolite and other samples (non-minerals, which also decompose on ignition with loss of water.

Closest to the proposed technical essence and the achieved result is a method

determination of iron hydroxides in the presence of hematite, based on the dissolution of iron hydroxides with 1: 1 diluted phosphoric acid with the addition of Nora salt, filtering the resulting solution and determining the inconsequence of hydroxides in the filtrate 2.

The method gives errors up to 1020% abs. due to incomplete dissolution of hydroxides and partial dissolution along with iron hydroxides of hematite.

The aim of the invention is to improve the accuracy of the determination of iron hydroxides in the presence of hematite due to the selective dissolution of iron hydroxides.

Claims (1)

The goal is achieved by the fact that according to the method of determining iron hydroxides in the presence of hematite, including dissolving the sample, filtering the solution and determining iron hydroxides in the filtrate, the sample is pre-calcined and dissolved with a solution of sulfuric acid for 20-30 minutes. When calcining a sample of iron hydroxide, having a varied composition (goethite HFeOj), hydrogetite, lepidocrocite FeO (OH), etc., are dehydrated to iron oxide, which upon subsequent dissolution of the sample by 23–27 th sulfuric acid solution for 20-30 The min is selectively separated from the natural iron oxides (hematite martite), also contained in a canopy. The selected conditions for dissolving the calcined support make it possible to most selectively and completely dissolve iron oxides obtained as a result of calcining iron hydroxide. At the same time, the natural iron oxides contained in the sample remain in the insoluble residue. Figure 1 shows the iron content of hydroxides determined in the filtrate, depending on the concentration of the solvent; Fig. 2 shows the same from the time of sample dissolution (the dotted line on the graphs shows the iron content of hydroxides calculated on the basis of complete and thermal analyzes of the samples under study). The optimal conditions for dissolving the calcined sample were established: solvent - 23-27% solution of sulfuric acid, dissolution time 20-30 minutes. When the concentration of the solvent is below 231%, the iron oxides are not dissolved, resulting from the calcination of the hydroxides of iron, which leads to an underestimation of the results. With an increase in the solvent concentration above 27%, hematite partially passes into the solution, which leads to an increase in the results on the iron content of hydroxides. When the time of dissolution of the sample is less than 20 minutes, iron oxides resulting from calcination are not dissolved, and when the time of dissolution of the sample is more than 30 minutes, part of the iron of hematite passes into the solution. In both cases, the results of the determination of iron hydroxide are distorted. EXAMPLE A portion of material 0.25 g, crushed to 0.08 mm, is placed in a porcelain crucible and calcined at 300–350 ° C for 3 hours. Then, the calcined sample was transferred into a 250 ml flask, 50 ml of a 23-271% solution of sulfuric acid were poured, put into a boiling water bath and dissolved for 20-30 min, periodically stirring the contents of the flask. The solution is filtered into a 250 ml flask. The precipitate and filter are washed 5-7 times with water. The total iron content in the filtrate corresponds to the iron content of hydroxides; the hematite iron is determined in the insoluble residue. The table shows the iron content of hydroxides, established by the calculation method on the basis of complete and thermal analyzes by known and proposed methods. As can be seen from the table, the exact analysis performed by the proposed method is, on average, three times higher than that known. The proposed method is simple in execution and allows quite accurately (the accuracy of the method is 0.5-1.0 abs.) To determine the iron hydroxide in a wide range from 3.1 to 59.51. Compared with the calculated method of determining iron hydroxides based on complete and thermal analyzes, which require 2-5 working days, the proposed method provides a direct determination of iron hydroxides in 5 hours. Formula of the invention sample size, filtering the solution and subsequent analysis in the filtrate of iron hydroxides by one of the known methods, which, in order to increase the selectivity of the dissolution of the hydroxide iron harvesting, the sample was preliminarily calcined, and the solution was dissolved in a 23–27 solution of sulfuric acid for 20–30 min. Sources of information taken into account in the examination 1. Fedorova M.N. Phase chemical analysis of ferrous metals ores and their products. 1972, pp.53-55. 2, GInchuk N.Kh. Phase chemical analysis of ores and minerals. 1962, s.PYY. 60 thirty W 152025 Concentration // $ 0 S5% ЪО Fig. / 60